I disagree. Wheadon is famous for doing nasty things to characters early in the show's run. I fully expect somebody to be killed or turn out to be a traitor by February sweeps.
Who?
Buffy: First major death is Angel in the season 2 finale but he gets back in season 3, Buffy "dies" for a split second which leads to another Slayer being called. The only major deaths are Buffy's mom (one of the most awesome episodes), Tara and Anya in the show finale
Angel - Riley early on because the actor wanted out of the show i believe, Cordelia in season 4 (same reason) and Fred (season 5 or already season 4)
Dollhouse: No major deaths in the show but then i missed most of season 2
Firefly: Cancelled too soon but given a normal run there were 3 potential couples (Mal/Inara, Zoe/Wash and Simon/Kaylee) to choose from and we know Whedon just loves to rip apart happy fan favorite couples so i guess it would have happened sooner or later (as evident from Serenity with 2 crew deaths)
Traitor.. not the same as death of a beloved character. As far as i can tell there
are no beloved characters in the show (hopefully yet) and i guess killing off Skye would set of a thank you storm in the internet

(personal bias included). This is the main problem with the entire show.. we just don't care about any of the characters maybe with the exception of Coulson but since he's the central figure of the show he's immune to death (pun also included). There are bits and pieces here and there that make me like some of the characters or get a fresh angle on them.. FitzSimmons sure have grown a bit in the last few episodes and the one where Ward and Simmons (or was it Fitz) went on a solo mission was also quite good characterwise but overall the show is just too bland.
I don't like to bring up Firefly (i'll do it anyway) but that show had about the same run time now as Shield (a few more episodes but that's besides the point) and we were deeply engaged with the crew to a point i have rarely seen in most shows after such a short while. Hell.. i was done after the pilot episode which had more effortless character explanation than the whole Shield run so far.
I hope the producers pay very close attention to the feedback and try to turn the ship around.. they are improving but the show is still mediocre when everyone was expecting another "Whedon must see TV appointment level" show (especially after he totally rocked the Avengers movie). Maybe that was the problem but shows didn't start with such a big built in audience and still managed to hit the ground running.